It is desirable that semiconductor devices such as microcomputers applied, for example, to in-vehicle LSI products are low-power-consumption semiconductor devices. Accordingly, an MIS transistor that is included in a semiconductor device is required to allow a low-voltage operation, have a large driving current, and have a low leakage current.
A conventional low-power-consumption MIS transistor has been proposed in which a subthreshold leakage current is reduced by increasing the concentration of a channel impurity-doped layer, thereby setting a threshold voltage to higher value.
A semiconductor device has also been proposed in which a short-channel effect is reduced by disposing a pocket impurity-doped layer between a source diffusion layer and a channel region and between a drain diffusion layer and a channel region so as to suppress punch-through between a source and a drain regions, punch-through being accompanied by the short-channel effect.
A semiconductor device has been further proposed in which a junction field between a source/drain region or a region extending therefrom and a channel impurity-doped layer or a pocket impurity-doped layer is reduced by forming the pocket impurity-doped layer to have an overlapping structure, thereby decreasing a junction leakage current. A technique for forming the pocket impurity-doped layer is disclosed in, for example, Japanese Laid-Open Patent Publication No. 2007-173421 and Japanese Laid-Open Patent Publication No. 2007-335704.
Recently, there has been an increasing desire for ultra-low-power consumption, and the further reduction of a junction leakage current has been sought. In addition, there is also a desire for further increasing a driving current and further improving a short-channel effect.